The invention relates to a device and a corresponding method for reducing an electromagnetic field, e.g. during the inductive charging of a vehicle.
Vehicles having an electric drive typically have a battery in which electrical energy for operating an electric machine of the vehicle can be stored. The battery of the vehicle can be charged with electrical energy from a power supply network. For this purpose, the battery is coupled to the power supply network in order to transfer the electrical energy from the power supply network into the battery of the vehicle. The coupling can be effected in a wired manner (via a charging cable) and/or wirelessly (on the basis of an inductive coupling between a charging station and the vehicle).
One approach for automatic, wireless, inductive charging of the battery of the vehicle consists in transferring the electrical energy to the battery from the ground to the underbody of the vehicle by means of magnetic induction via the underbody clearance 120. This is illustrated by way of example in FIG. 1. In particular, FIG. 1 shows a vehicle 100 having an energy store 103 for electrical energy (e.g. having a chargeable battery 103). The vehicle 100 includes a so-called secondary coil 102 in the vehicle underbody, wherein the secondary coil 102 is connected to the energy store 103 via an impedance matching (not shown) and a rectifier 101.
The secondary coil 102 can be positioned above a primary coil 111, wherein the primary coil 111 is fitted e.g. on the floor of a garage. The primary coil 111 is connected to a power supply 110. The power supply 110 can be a radiofrequency generator which generates an AC (alternating current) current in the primary coil 111, whereby a magnetic field is induced. Given sufficient magnetic coupling between primary coil 111 and secondary coil 102 via the underbody clearance 120, the magnetic field induces a corresponding voltage and thus also a current in the secondary coil 102. The induced current in the secondary coil 102 is rectified by the rectifier 101 and stored in the energy store 103 (e.g. in the battery). In this regard, electrical energy can be transferred wirelessly from the power supply 110 to the energy store 103 of the vehicle 100.
The AC current in the coils 111, 102 typically generates an electromagnetic field which can have an interfering effect on the environment. By way of example, the electromagnetic field can impair functions of the vehicle 100 or of neighboring vehicles 100. The present document addresses problem of neutralizing and/or reducing the electromagnetic field generated during inductive charging (e.g. compensating for it in specific regions). Moreover, the present document addresses the problem of reducing and possibly eliminating the influence of the electromagnetic field generated during inductive charging on specific functions of the vehicle 100 and/or of a neighboring vehicle.
The problem is solved by an apparatus and method in accordance with embodiments of the invention.
In accordance with one aspect, a control unit for a vehicle is described. The vehicle may be e.g. a double-track or a single-track vehicle. In particular, the vehicle may be an automobile, a truck or a motorcycle. The vehicle may include an electric machine which may be used to drive the vehicle. Furthermore, the vehicle may include an energy store for storing electrical energy. Moreover, the vehicle may have a charging coil which causes an electromagnetic interference field.
The control unit is designed to determine one or more properties of an electromagnetic interference field, caused in particular by inductive charging. However, the interference field may also be caused by other power electronics of the vehicle. The one or more properties of the interference field may include, in particular, a frequency of the interference field and/or one or more field strength values of the interference field at one or more locations around and/or in the vehicle. The frequency of the interference field may be in the LF range, i.e. in the long-wave range between 30 kHz and 300 kHz. The field strengths may decrease with increasing distance from the charging coil which generates the interference field.
The one or more properties of the interference field may be determined on the basis of measurement values which were detected e.g. by one or more sensors of the vehicle. Alternatively or supplementarily, the one or more properties may be predefined and be stored on a storage unit of the vehicle. This may be the case particularly if the interference field is generated by a charging coil (i.e. the secondary coil) of the vehicle. In other words, this is the case particularly if the interference field is generated by an inductive charging process of the vehicle. The control unit may then be designed to access the storage unit and thus to determine the one or more properties of the interference field.
The control unit is further designed to cause one or more transmitting units of the vehicle to emit an opposing field which reduces a field strength of the interference field in a first region around and/or in the vehicle. The opposing field may be determined and emitted in such a way that a destructive interference results from a superimposition of the opposing field with the interference field in the first region. The first region may include surroundings of the one or more transmitting units which directly adjoin the one or more transmitting units.
The interference field (at least in the first region) may be neutralized by the emission of an opposing field. This results in a reduction of the electromagnetic radiation in the first region. Furthermore, this has the effect that vehicle functions (e.g. an access function) the first region are not impaired by the interference field.
A transmitting unit may be a transmitting unit which is used in a dedicated manner for reducing and/or cancelling the interference field in the first region. Alternatively or supplementarily, recourse may be had to a transmitting unit which is already used in the vehicle for other vehicle functions (in particular for an access function to the vehicle). The vehicle may be designed to provide a “keyless” access function to the vehicle. The access function may be a function which enables a user to open a door of the vehicle without actuating a vehicle key. For this purpose, the access function may include an exchange of authentication signals between the vehicle and a vehicle-external authentication unit (e.g. the vehicle key).
The transmitting unit may be designed to transmit an authentication signal to the authentication unit. The interference field may interfere with the transmitted authentication signal and thereby impair the access function. The opposing field may neutralize the interference field in the first region, such that the exchange of authentication signals in the first region may proceed without interference, and the access function can thus function without interference.
The control unit may be designed to cause the transmitting unit to emit a superimposition of the opposing field and an authentication signal. In other words, the transmitting unit may be used both to neutralize the interference signal and to provide the access function. As a result, the interference signal may be neutralized in a cost-effective manner since recourse may be had to vehicle components already present.
The control unit may be designed to alter the opposing field in order to reduce the interference field in a second region around and/or in the vehicle. In this case, the second region may include at least one location around and/or in the vehicle which is not contained in the first region. By way of example, the control unit may be designed to cause the emission of an opposing field, such that the region with reduced field strength of the interference field follows the authentication unit, and an interference-free access function of the vehicle can be ensured at any arbitrary location around and/or in the vehicle.
The vehicle may have a multiplicity of transmitting units at different locations of the vehicle. Transmitting units may be arranged for example at the sides, in the front region and/or in the rear region of the vehicle. The opposing field for reducing the interference field in the first region may be generated by a plurality of transmitting units. Alternatively or supplementarily, the control unit may be designed to cause the multiplicity of transmitting units to emit a corresponding multiplicity of opposing fields which reduce the field strength of the interference field in a corresponding multiplicity of regions. The multiplicity of regions may be arranged at different locations of the vehicle in a manner corresponding to the multiplicity of transmitting units. In this regard, if appropriate, comprehensive neutralization of the interference field (e.g. at different points in time) may be made possible.
In accordance with a further aspect, a method for neutralizing an electromagnetic interference field caused by the inductive charging of a vehicle is described. The method includes determining one or more properties of the interference field. Furthermore, the method includes emitting an opposing field (e.g. by causing a transmitting unit of the vehicle to emit the opposing field) which reduces and/or cancels a field strength of the interference field in a first region around and/or in the vehicle.
In accordance with a further aspect, a software (SW) program is described. The SW program may be designed to be executed on a processor and thereby to perform the method described in this document.
In accordance with a further aspect, a storage medium is described. The storage medium may have stored thereon an SW program designed to be executed on a processor and thereby to perform the methods described in this document.
It should be taken into consideration that the methods, devices and systems described in this document can be used both by themselves and in combination with other methods, devices and systems described in this document. Furthermore, any aspects of the methods, devices and systems described in this document may be combined with one another in diverse ways.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.